python dict, if, get, and try-except

content

To fetch a value from dictionary, when do we use if, or get, or try-except

d = {'a': 1}
 
if 'a' in d:
	d['a'] += 1
else:
	d['a'] = 1
 
d['a'] = d.get('a', 0) + 1
 
try:
	d['a'] += 1
except KeyError:
	d['a'] = 1

get has been my favorite
- mainly because of its syntax
- but i haven’t really thought about this question
performance wise, get is actual slow
when we write code, performance is usually not our top priority
it’s more about readability and the 语义 (underlying meaning) of these different methods
- the most obvious is try-except
  - when we use try-except, we are implicitly implying that this is an error (Exception)
- when we just want to set a default value, get makes the most sense
- if allows us to do something that get doesn’t:

if 'x' in d:
	d['x'] += 1
else:
	call_a_function()